Flight tests of an intermediate wing sweep angle for the Rockwell B-1B bomber are entering an intensive phase at Edwards AFB, California, as part of the US Air Force's plan to broaden the aircraft's capability.

The tests are aimed at evaluating flying qualities with a 45° wing sweep to allow the B-1B to operate at airspeeds "compatible with other types of aircraft in a strike force package", says project manager Capt Duncan Dversdall of the 419th Flight Test Squadron.

The B-1B is now cleared to fly with the wing in the 15°, 25°, 55° and 67.5° positions, but the new angle was requested by Air Combat Command as part of efforts to increase the efficiency of the bomber at cruise altitudes and to enable it to be more easily integrated with other combat types on combined missions.

Wing sweep positions outside the current angles have not been cleared for continuous manoeuvring flight. As a result, when a pilot moves the wings from, for example, 25° to 55°, he must make the transition through the intermediate position without stopping and "while observing strict manoeuvring limits", says the USAF.

Planning for the project began in April last year and work to modify the test aircraft started in October that year. The first test flight was performed in April, but so far only 6h of a planned 50h effort have taken place. "The bulk of flight testing runs through from mid-July to mid-September," says the USAF.

Following completion of the test programme, the 419th will submit its recommendations to the B-1B systems programme office (SPO). Pending a successful conclusion, the SPO is expected to authorise updating of the B-1B technical manuals and the new sweep angle will become operational around mid-1999, says the USAF.

The angle will be tested over the operating envelope at various altitudes and speeds, ranging from the edge of stall at certain weights to a top speed of Mach 0.95.

Source: Flight International